Making Software ready for Retina Display - Why is this necessary?

Question

Now that the new Macbook Pro is coming out with a Retina Display, there are a lot of resources out there on how to make Mac apps and now even websites "Retina Display Friendly". Even Google is updating Chrome for Retina Display...

Why is this necessary at all? From what I understand, Retina Display is just a higher resolution screen. Right?

I thought when you develop gui's for desktop software and develop websites, you are developing something that is supposed to work and scale properly with virtually any resolution... When you resize an app's window, or display it on a higher or lower resolution display, it is supposed to scale and display properly.

So why are these people coming out with guides on how to make something look good on a Retina Display? Shouldn't it already look fine by default? Is there something about Retina Display that I'm not understanding?

And for the record, I'm not talking about iPhone 4 Retina Display. Most iOS dev's make their apps with fixed position elements since they know the screen's won't change size/shape. So I understand the importance of developing an app to look good on the iPhone 4/s vs 3g/s.

Answer 1

I thought when you develop gui's for desktop software and develop websites, you are developing something that is supposed to work and scale properly with virtually any resolution... When you resize an app's window, or display it on a higher or lower resolution display, it is supposed to scale and display properly (StackOverflow, for example, uses a 960px-wide container).

From a web developer standpoint, you are often asked to develop fixed-width websites (ranging from normally 940 to 1000 pixels wide), and they don't get to scale at all. There are a lot of websites like this and many apps just aren't designed to increase in size.

Also, apps that do grow in size usually expect that a bigger resolution also means a bigger screen, so they simply stretch the main application panels and are done with it.

Now, consider static elements, like a 150x50 button that says 'Click me'. This button is not intended to become bigger and is perfectly acceptable on a regular 1440x900 display. Now the retina screen comes in with its 2580x1800 resolution. The app sees the resolution change but it thinks "Hey, that user must have a huge screen" so it keeps the button the same size.

The problem that now occurs is that the button, because both resolutions apply to the same 13" screen, is now appearing to be a fraction of the size of the original button. Depending on your user vision, he might not be able to read the text on it, and might have a hard time clicking it, depending on the mouse settings.

To fix that problem, Apple and Microsoft used two different solutions:

• Microsoft decided to tell the app the display had a 2580x1800 resolutions, but that the user wanted to have everything scaled to 200 dpi. This means that, if an app does not follow the guidelines, it will look smaller. Many apps simply ignore the DPI settings (though this might change with Windows 8);
• Apple decided to report to apps that the resolution of the monitor was 1440x900, but that it could display higher-resolution elements if asked to; This means that apps existing before the new retina settings will appear to be the same size as before for the end-user (with added benefits like crisper text if they use the default Apple APIs), but that they can decide to provide high-DPI images that will look much better on the display.

Both solutions requires apps to be aware that the display is high-DPI ('retina'), but the way Apple handled it means the static websites and apps mentioned earlier will keep looking just fine, except they wont have super-crisp, high-resolution images to use. And, to opt-in to the retina features, they have to provide 200x200 images for a 100x100 canvas, for example, and Apple will take care of the rest.

Answer 2

With the Retina display apps don't actually scale like they're being resized, all the controls are resized to be twice as big. If an app would be scaled normally, not by scaling all the controls, etc. you wouldn't see anything, because everything would be too small. It's the same difference between a Retina and a lower-resolution display as on the iPhone 3GS / iPhone 4.

An example:

These images are actually the same size, just the pixel densities differ.

And here's how it looks not properly scaled (using some app to disable proper scaling): http://cloudmancer.com/images/trueretina.jpg